Copper-cobalt bimetallic phosphide heterojunction material and preparation method and application thereof

Abstract

The invention relates to a copper-cobalt bimetallic phosphide heterojunction and a preparation method and application thereof.The preparation method comprises the following steps that 1, pretreated foamy copper is soaked in an ammonium persulfate and sodium hydroxide solution, and the substance serves as a strong oxidant and is used for reacting to form copper hydroxide; (2) mixing cobalt nitrate hexahydrate with methanol, and putting copper hydroxide to react for two days; 3) adding dimethylimidazole for continuous reaction, and then washing, drying and phosphorizing at room temperature; compared with the prior art, the preparation method is simple in process and low in cost; the prepared catalyst has a heterojunction nanowire array structure, more active sites are provided, charge redistribution at a phosphide heterojunction interface is promoted by electron directional movement, the electron structure of the catalyst can be adjusted, and adsorption energy of reactants and intermediates on the active sites can be changed, so that reaction kinetics is promoted. The catalyst product is mainly ammonia gas, is good in stability and can be repeatedly used for multiple times.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalysts and relates to a copper-cobalt bimetallic phosphide heterojunction material (Cu3P@CoP / CF) and a preparation method and application thereof, and in particular to a copper-cobalt bimetallic phosphide heterojunction material and a preparation method thereof and application thereof in a reaction of removing nitrate from water to produce ammonia. Background Art

[0002] The Earth is primarily covered by water, of which only approximately 2% is freshwater. Freshwater resources are crucial for economic growth, human health, and the environment. However, with industrial advancement and social development, pollution of surface and groundwater poses a serious threat to aquatic ecosystems and society. Nitrogen, one of the five elements in cellular biomass, plays a vital role in the life processes of organisms. The continuous development and utilization of nitrogen resources by humans has led to global environmental pollution and an energy crisis. In particular, the increasing use of fertilizers and industrial wastewater has released large amounts of nitrate into surface and groundwater. Slow natural denitrification processes are unable to effectively remove excess nitrate and its derivatives, which pose certain risks to the environment and human health. First, when nitrogen concentrations in water bodies are too high, they can cause eutrophication, which in turn can lead to environmental pollution such as red tides. Second, excessive nitrate intake can cause serious illnesses such as blue baby syndrome and seriously harm human health. In addition, other derivatives produced during the nitrogen cycle also pose a huge threat to human health. For example, nitrite is a carcinogenic pollutant that can oxidize the divalent iron ions in hemoglobin into trivalent iron ions, thereby affecting the oxygen transport capacity of red blood cells.

[0003] Excessive nitrate nitrogen pollution in water bodies has become an urgent problem that needs to be addressed. Currently, traditional technologies involving chemical, photochemical, physical, and biological treatment of nitrates have been widely used. Although photocatalysis is simple to operate, the recombination of photogenerated carriers during the photocatalytic reaction greatly reduces the photocatalytic activity. Biological denitrification technology can achieve nitrogen removal from various types of wastewater under appropriate conditions. However, this technology also has certain limitations, such as sludge production, easy spread of pathogenic bacteria, and low efficiency. As for physical removal methods (such as reverse osmosis and ion exchange), their core function is to transfer or concentrate nitrates, not to remove them. Therefore, secondary brine containing nitrates is produced during the treatment process, which increases the subsequent treatment costs. In addition to directly removing excess nitrogen pollution in water, converting it into ammonia for further use is also a current research focus. As an important chemical raw material and energy carrier, ammonia is one of the important energy carriers due to its high energy density, zero carbon emissions, and easy storage and transportation. However, over the past 100 years, the traditional Haber-Bosch (HB) ammonia synthesis process has consumed 1% to 2% of global energy and produced 1% of global CO2. This is primarily due to the high nitrogen-nitrogen triple bond strength and the use of non-clean energy sources. Therefore, the aforementioned method of using nitrate as a nitrogen source and converting it into ammonia using clean energy has become an important part of chemical energy storage.

[0004] Electrocatalytic reduction denitrification primarily relies on electron transfer on the cathode catalyst surface to reduce nitrates adsorbed on the catalyst surface. Generally, the electrocatalytic reduction reaction occurs within the hydrogen production potential range of the cathode catalyst. Because this technology requires no additional reducing agents, offers excellent denitrification capabilities, is resistant to interference, is environmentally friendly, and produces no byproducts that could cause secondary pollution, it is considered a highly promising wastewater treatment technology.

[0005] Current challenges in the electroreduction of nitrates primarily stem from multiple electron / proton transfer steps, low ammonia selectivity, and a competitive hydrogen evolution reaction (HER). Therefore, the design and development of advanced electrocatalysts capable of efficiently promoting the electrocatalytic reduction of nitrates to ammonia is crucial. Copper-based catalysts have been recognized as one of the most promising catalysts for the electrochemical conversion of nitrates to ammonia. However, weak hydrogen adsorption on the Cu surface limits the electroreduction of nitrates, requiring only negative potentials to achieve sufficient *H coverage to maintain significant surface hydrogenation rates, resulting in satisfactory NH3 production rates and FE. Notably, efficient nitrate reduction catalysts generally require both good nitrate adsorption and sufficient water-splitting capacity to provide sufficient protons and reduce the overpotential. Therefore, the rational regulation and design of Cu-based catalysts to activate their hydrogenation capacity is crucial for improving the electrocatalytic reduction of nitrates. Research has shown that first-row transition metal phosphides, alloys of metal and phosphorus, are active catalysts for hydrotreating (HDX, X = S, O, N) and hydrogenation reactions. The metal centers of partially positively charged phosphides effectively adsorb nitrate and nitrite anions, while the partially negatively charged phosphides, namely phosphorus, serve as proton acceptor centers. Furthermore, copper-based composites composed of copper and other materials exhibit excellent selectivity for the reduction of nitrate to ammonia. Co-based catalysts exhibit strong catalytic activity and NH3 selectivity in the electroreduction of nitrate. Numerous Co-based catalysts have been reported for the electroreduction of nitrate, achieving excellent electrocatalytic ammonia synthesis. Heterojunctions, as interfacial structures, are a promising strategy for improving the catalytic performance of materials. They not only overcome the inherent shortcomings of each material but also generate novel properties due to interfacial effects. In particular, heterogeneous nanostructures with built-in electric fields can promote interfacial charge transfer during electrocatalysis and effectively influence the adsorption of reactants and intermediates. Furthermore, synergistic electron transfer interactions between different metal species can alter the electronic states of the metal atomic centers, thereby optimizing the adsorption energies of important reaction intermediates. Therefore, it is reasonable to construct copper-cobalt bimetallic phosphides with heterojunction interfaces to enhance the catalytic activity of nitrate electroreduction.

[0006] Prior art CN114318408A discloses a self-supporting Cu3P-based heterojunction electrocatalyst, its preparation method, and application. The electrocatalyst is composed of any one of Fe2O3, Ni2P, and CoP coated on self-supporting Cu3P nanowires. The preparation method comprises the following steps: electro-oxidizing cleaned copper foam in an alkaline solution to obtain self-supporting Cu(OH)2 nanowires; dehydrating the self-supporting Cu(OH)2 nanowires in a muffle furnace to obtain self-supporting CuO nanowires; immersing the self-supporting CuO nanowires in a mixed solution of 2-methylimidazole, nitrate, methanol, and water, allowing a liquid-phase reaction at room temperature to obtain a self-supporting precursor; and phosphating the self-supporting precursor with PH3 generated by sodium hypophosphite under inert gas protection at 150-210°C. This technical solution has the advantages of simple process, mild conditions, and low energy consumption. The prepared self-supporting Cu3P-based heterojunction electrocatalyst has a controllable structure and is applied to the electrolysis of water to catalyze hydrogen and oxygen evolution, exhibiting high activity and stability. However, this type of material has low ammonia synthesis efficiency in the reaction of removing nitrates from water to produce ammonia, and the process complexity and production cost are high. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method and application of a copper-cobalt bimetallic phosphide heterojunction material, which is used to solve the problems of low efficiency and poor stability of existing catalyst materials for removing nitrate from water to produce ammonia. The present invention relates to a nitrate reduction to ammonia (NO3RR) technology, which promotes the hydrogenation treatment and hydrogenation reaction during the electrochemical reduction reaction of nitrate through the synergistic catalytic effect between the copper and cobalt dual active sites. It has significant advantages in the following aspects: 1. Multiple active site design, by optimizing the material structure, it can simultaneously adsorb and activate multiple intermediates in the nitrate reduction process (such as NO3 - , NO2, etc.), achieving efficient proton-electron cooperative transfer and improving ammonia synthesis efficiency; 2. Simplifying the preparation process, using water-ethanol to pretreat the foam copper substrate, eliminating the need for traditional alkaline solution electro-oxidation steps, significantly reducing process complexity and production costs; 3. Interfacial catalytic synergy, the functionalized interface design enhances reaction mass transfer and electron transfer, further improving catalytic stability and selectivity.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] A first aspect of the present invention provides a method for preparing a copper-cobalt bimetallic phosphide heterojunction material, comprising the following steps:

[0010] 1) Immersing the copper foam with Cu(OH)2 grown thereon in a cobalt salt solution for a primary reaction; then adding 2-methylimidazole for a secondary reaction to obtain an intermediate product;

[0011] 2) placing a phosphorus source and an intermediate product upstream and downstream of a flowing phosphating atmosphere, respectively, and heating the phosphorus source and the intermediate product to obtain a copper-cobalt bimetallic phosphide heterojunction material (Cu3P@CoP / CF).

[0012] In some specific embodiments, in step 1), the method for preparing the copper foam grown with Cu(OH)2 comprises: immersing the copper foam in an aqueous solution containing (NH4)2S2O8 and NaOH to obtain.

[0013] In some specific embodiments, the copper foam is pretreated before impregnation, comprising: adding the copper foam to a mixed solution of concentrated hydrochloric acid and water in a volume ratio of 1:3, ultrasonically treating the copper foam at room temperature for 5 to 10 minutes, then adding the copper foam to ethanol, ultrasonically treating the copper foam at room temperature for 5 to 10 minutes, washing, and drying.

[0014] In some specific embodiments, the feed ratio of the foamed copper, (NH4)2S2O8 and NaOH is (80-120) mg: (1.2-1.4) mmol: (10-40) mmol;

[0015] During the immersion, the immersion temperature is 20-30° C., and the immersion time is 10-20 minutes.

[0016] In some specific embodiments, in the aqueous solution, the concentration of (NH4)2S2O8 is 3-8 wt%, the concentration of NaOH is 10-20 wt%, and the concentration of water is 60-80 wt%.

[0017] In some specific embodiments, in step 1), the cobalt salt is cobalt acetate or cobalt nitrate;

[0018] The feeding ratio of the foam copper and cobalt salt grown with Cu(OH)2 is (80-120) mg: (0.5-1.5) mmol.

[0019] In some specific embodiments, in step 1), in the primary reaction, the reaction temperature is 20-30° C., and the reaction time is 24-48 h.

[0020] In some specific embodiments, in step 1), the molar ratio of the cobalt salt to dimethylimidazole is 1:(5-10).

[0021] In some specific embodiments, in the reaction raw material system of the secondary reaction, the concentration of the cobalt salt is 0.5-3.0 wt %, the mass concentration of dimethylimidazole is 1.0-10 wt %, and the mass concentration of water is 60-80 wt %.

[0022] In some specific embodiments, in step 1), in the secondary reaction, the reaction temperature is 20-30° C., and the reaction time is 2-6 h.

[0023] In some specific embodiments, step 2) includes: placing a phosphorus source upstream of a quartz tube of a tubular furnace, placing an intermediate product downstream of the quartz tube, and heating the phosphorus source and the intermediate product under inert atmosphere to obtain a copper-cobalt bimetallic phosphide heterojunction material.

[0024] In some specific embodiments, in step 2), the phosphorus source is NaH2PO2,

[0025] The feed ratio of the phosphorus source to the intermediate product is 50-200 mg:90-140 mg.

[0026] In some specific embodiments, in step 2), during the calcination, the phosphating atmosphere is an inert gas, the calcination temperature is 300-350° C., and the calcination time is 2-4 hours.

[0027] A second aspect of the present invention provides a copper-cobalt bimetallic phosphide heterojunction material prepared by the method described in any one of the above items.

[0028] A second aspect of the present invention provides an application of the copper-cobalt bimetallic phosphide heterojunction material as described above, comprising using the copper-cobalt bimetallic phosphide heterojunction material for an electrocatalytic denitrification reaction.

[0029] Since copper-based materials can easily inject d electrons into NO3 - The lowest unoccupied molecular orbital (LUMO) π* orbital of α-HNO3 is considered to be highly active for nitric acid reduction. Although this active site can enhance the NO3 - adsorption and conversion, but a large amount of by-product NO2 - Easily detected, this defect can be caused by poor hydrogenation.

[0030] Transition metal phosphides are alloy materials of metal and phosphorus. The metal centers of some positively charged phosphides can effectively adsorb nitrate and nitrite anions, while the negatively charged phosphides, namely phosphorus, are proton acceptor centers, which promote the hydrogenation treatment and hydrogenation reaction during the electrochemical reduction reaction of nitrate ions.

[0031] The formation of heterojunction nanowire arrays provides more active sites, and the synergistic catalytic effect between the copper and cobalt dual active sites is beneficial to the intermediate *NO x The directional movement of electrons promotes the charge redistribution at the phosphide heterojunction interface, which can adjust the electronic structure of the catalyst and change the adsorption energy of reactants and intermediates on the active site, thereby promoting the reaction kinetics.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention features a simple process and low cost. The prepared catalyst has a heterojunction nanowire array structure, which provides more active sites. The phosphorus p orbital can effectively combine with hydrogen in water to form active hydrogen (*H), promoting the hydrogenation reaction. The synergistic catalytic effect between the copper and cobalt dual active sites regulates the thermodynamic energy barrier between the intermediates *NOx and *H. The catalyst also exhibits good dispersibility of catalytic components, high catalytic activity, a high ammonia production rate, excellent stability, and is reusable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The scanning electron microscope image (SEM image for short) (a) and the transmission electron microscope image (TEM image for short) (b) of the electrocatalyst prepared in Example 1 are shown.

[0035] Figure 2 These are the SEM images (cd) obtained after 150 cycles in Example 2.

[0036] Figure 3 The scanning electron microscope image (SEM image for short) (a) and the transmission electron microscope image (TEM image for short) (b) of the electrocatalyst in Comparative Example 1 are shown.

[0037] Figure 4 The scanning electron microscope image (SEM image for short) (a) and the corresponding local enlarged image (b) of the electrocatalyst prepared in Comparative Example 2 are shown.

[0038] Figure 5 The scanning electron microscope image (a) and the corresponding local magnified image (b) of the electrocatalyst prepared in Comparative Example 3.

[0039] Figure 6 (a) Schematic diagram of the synthesis route of the copper-cobalt bimetallic phosphide heterojunction (Cu3P@CoP / CF) of the present invention, (b) SEM image, (c) magnified SEM image, (d) TEM image of the Cu3P@CoP / CF prepared in Example 1, and (e) summary of the performance results of the prepared heterojunction sample electrode after 150 long cycles. DETAILED DESCRIPTION

[0040] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0041] In the following examples, unless otherwise specified, raw materials, reagents or processing techniques are all conventional commercially available products or conventional processing techniques in the art.

[0042] In the following examples, potassium hydroxide, sodium hydroxide, dimethylimidazole, and cobalt nitrate hexahydrate were purchased from Shanghai Titan Technology Co., Ltd.; potassium nitrate was purchased from Sinopharm Chemical Reagent Co., Ltd.; and ammonium persulfate and sodium hypophosphite were purchased from Aladdin Reagent Biochemical Technology Co., Ltd.

[0043] Example 1:

[0044] A copper-cobalt bimetallic phosphide heterojunction material, such as Figure 6 As shown, the preparation method comprises the following steps:

[0045] (1) Cu(OH)2 nanowire arrays were controllably grown on the surface of copper foam by chemical oxidation. Before preparing the material, the copper foam was pretreated by ultrasonic cleaning in distilled water and ethanol for a few minutes. Then, 100 mg of 1×1 cm 2 Copper foam was immersed in 10 mL of an aqueous solution containing 296 mg of (NH₄)₂S₂O₄ and 1 g of NaOH. Over time, the surface color of the copper foam changed from yellow to blue, indicating the formation of Cu(OH)₂. After 20 minutes, the copper foam, which had grown Cu(OH)₂, was removed. The foam was rinsed with deionized water and ethanol, then dried in a vacuum oven. The resulting product was designated Cu(OH)₂ / CF.

[0046] (2) Take 800 mg of 2-methylimidazole and dissolve it in 25 mL of methanol solution. The solution at this time is recorded as solution A. Take 249 mg of Co(Ac)2·4H2O and dissolve it in 25 mL of methanol solution. The solution at this time is recorded as solution B. Then add 110 mg of Cu(OH)2 / CF to solution B, seal it with aluminum foil, and react at room temperature for 48 hours. Then add solution A to solution B containing Cu(OH)2 and react at room temperature for 2 hours. Finally, take out the purple sample from the above solution, rinse it with methanol, and then dry it in a vacuum oven overnight to obtain ZIF-67@Cu(OH)2;

[0047] (3) Using the gas-solid phosphating method, 120 mg of ZIF-67@Cu(OH)2 was placed downstream of a tube furnace and 0.2 g of NaH2PO2 was placed upstream of the heating device. Under an argon (Ar) atmosphere, the temperature was increased to 300°C at a rate of 2°C / min and maintained for 2 h. The final product was cooled to room temperature under an argon atmosphere to obtain Cu3P@CoP / CF.

[0048] Figure 1 These are the SEM and TEM images of the catalyst prepared in this example. From the images, it can be seen that the heterojunction presents a nanowire array structure.

[0049] Figure 2This is a SEM image obtained after 150 cycles. The electrocatalytic denitrification test employed a three-electrode system with a prepared copper-cobalt bimetallic phosphide heterojunction electrode as the working electrode, a mercury / mercuric oxide electrode as the reference electrode, and a platinum sheet as the counter electrode. The test electrolyte consisted of 30 mL of a 1M sodium hydroxide solution containing 1400 mg / L nitrate nitrogen. The test method employed a time-current (it) curve, with a single test lasting one hour at room temperature and repeated 150 times. The SEM images before and after the reaction demonstrate that the catalyst material remained intact after the reaction.

[0050] Comparative Example 1

[0051] A copper-based phosphide heterojunction material, the preparation method of which differs from that of Example 1 only in that:

[0052] Step (2) was omitted, that is, the prepared Cu(OH)2 / CF was directly phosphated to obtain Cu3P / CF without adding cobalt nitrate hexahydrate. The rest of the process was the same as in Example 1.

[0053] Figure 3 The SEM and TEM images of the prepared catalyst show that the original Cu(OH)2 / CF nanowires evolve into Cu3P nanoclusters due to the phosphating effect.

[0054] Comparative Example 2

[0055] A cobalt-based phosphide heterojunction material, the preparation method of which comprises:

[0056] 1 mmol of Co(NO₃)₂·6H₂O, 0.3 g of NH₄F, and 0.5 g of urea were dissolved in 35 mL of deionized water and stirred for 30 minutes. The mixed solution and the treated cobalt (CoF) foam were then transferred to a 50 mL polytetrafluoroethylene (PTFE) reactor and reacted at 120°C for 6 hours. After the reaction, the Co(OH)₂ / CoF was removed, rinsed repeatedly with water and ethanol, and then dried under vacuum at 60°C until ready for use. Finally, NaH₂PO₂ powder and the Co(OH)₂ / CoF were placed upstream and in the center of the airflow of a tube furnace, respectively. The sample was heated at 300°C for 2 hours under an argon atmosphere at a heating rate of 2°C / min to obtain CoP / CoF.

[0057] Figure 4 These are the SEM and TEM images of the prepared catalyst. It can be seen from the images that CoP / CoF appears in the shape of a sea urchin.

[0058] Comparative Example 3

[0059] A cobalt-based phosphide heterojunction material, the preparation method of which differs from that of Example 1 only in that:

[0060] Omit step (1), that is, the pre-treated 1×1cm 2 The copper foam was rinsed with deionized water and ethanol, and then dried in a vacuum oven. Subsequently, the prepared CF was directly phosphated using the same method as step (3) of Example 1 to obtain Cu3P / CF. The rest of the process was the same as Example 1.

[0061] Figure 5 is the SEM image of the prepared catalyst.

[0062] Application Examples

[0063] According to Example 1 and Comparative Examples 1, 2, and 3, electrocatalytic denitrification tests were carried out under the same conditions, specifically:

[0064] A three-electrode test system was used, with the prepared electrode sheet as the working electrode, a mercury / mercury oxide electrode as the reference electrode, a platinum sheet as the counter electrode, and a test electrolyte of 330 mL of a 1 M sodium hydroxide solution containing 1400 mg / L nitrate nitrogen. The test method was a time-current (it) curve test with a test time of 1 hour and a test temperature of room temperature. After that, electrolysis was performed at different reaction times.

[0065] The electrocatalyst prepared by Example 1 and Comparative Examples 1-3 is subjected to laboratory electrocatalytic denitrification test, and electrolyte is respectively sodium nitrate containing 1400mg / L nitrate nitrogen and 1M sodium hydroxide mixed solution, and electrochemical workstation is used to measure denitrification and ammonia production effect. The concentration of ammonia in electrolyte is determined using indoxyl blue method, specifically: 2mL of A solution (4g sodium hydroxide, 5.42g salicylic acid and 5.42g sodium citrate solution are added in 100mL ultrapure water) is added in 2mL of reacted electrolyte, then, 200 μL of C solution (weighing 0.997g sodium ferrocyanide dihydrate and being dissolved in 100mL ultrapure water) and 1mL of B solution (taking 9mL of sodium hypochlorite and adding 96.93g ultrapure water) are sequentially added to the above-mentioned solution. After waiting for reaction 40min, reaction product mixed solution is tested in UV-visible spectrophotometer. The concentration of ammonium in the reaction solution can be determined because of the visible light absorption peak of ammonium at 655 nm. The test results of the ammonia generation rate and Faradaic efficiency of the electrocatalyst for one hour are shown in Table 1.

[0066] Table 1

[0067]

[0068]

[0069] As can be seen from Table 1, the catalysts prepared in Example 1 and Comparative Examples 1-3 exhibited excellent ammonia production rates and good ammonia Faraday efficiencies, wherein Example 1 had excellent ammonia production rates and good ammonia Faraday efficiencies.

[0070] In summary, the present invention provides a copper-cobalt bimetallic phosphide heterojunction material, the formation of which is conducive to the exposure of active sites and the rapid diffusion of bubbles, which provides favorable conditions for its long-term operation at high current density. The bifunctional active sites interact with each other, and the heterogeneous array skeleton can also realize the series catalysis between the two active sites.

[0071] The present invention offers a simple process and low cost. The formation of heterojunction nanowire arrays provides more active sites. The directed electron migration promotes charge redistribution at the phosphide heterojunction interface, modulating the catalyst's electronic structure and changing the adsorption energy of reactants and intermediates at the active sites, thereby promoting reaction kinetics. The catalyst product, primarily ammonia, is stable and reusable.

[0072] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-cobalt bimetallic phosphide heterojunction material, characterized in that: The following steps are involved: 1) Immersing the copper foam with Cu(OH)2 grown thereon in a cobalt salt solution for a primary reaction; then adding 2-methylimidazole for a secondary reaction to obtain an intermediate product; 2) placing a phosphorus source and an intermediate product upstream and downstream of a flowing phosphating atmosphere, respectively, and heating the phosphorus source and the intermediate product to obtain a copper-cobalt bimetallic phosphide heterojunction material.

2. The method for preparing the copper-cobalt bimetallic phosphide heterojunction material according to claim 1, characterized in that: In step 1), the preparation method of the copper foam with Cu(OH)2 grown thereon comprises: immersing the copper foam in an aqueous solution containing (NH4)2S2O8 and NaOH to obtain.

3. The method for preparing the copper-cobalt bimetallic phosphide heterojunction material according to claim 2, characterized in that: The feeding ratio of the foam copper, (NH4)2S2O8 and NaOH is (80-120) mg: (1.2-1.4) mmol: (10-40) mmol; During the immersion, the immersion temperature is 20-30° C., and the immersion time is 10-20 minutes.

4. The method for preparing the copper-cobalt bimetallic phosphide heterojunction material according to claim 1, characterized in that: In step 1), the cobalt salt is cobalt acetate or cobalt nitrate; The feeding ratio of the foam copper and cobalt salt grown with Cu(OH)2 is (80-120) mg: (0.5-1.5) mmol.

5. The method for preparing the copper-cobalt bimetallic phosphide heterojunction material according to claim 1, characterized in that: In step 1), in the primary reaction, the reaction temperature is 20-30° C., and the reaction time is 24-48 h.

6. The method for preparing the copper-cobalt bimetallic phosphide heterojunction material according to claim 1, characterized in that: In step 1), the molar ratio of the cobalt salt to dimethylimidazole is 1:(5-10).

7. The method for preparing the copper-cobalt bimetallic phosphide heterojunction material according to claim 1, characterized in that: In step 1), in the secondary reaction, the reaction temperature is 20-30° C., and the reaction time is 2-6 h.

8. The method for preparing the copper-cobalt bimetallic phosphide heterojunction material according to claim 1, characterized in that: In step 2), the phosphorus source is NaH2PO2, The feed ratio of the phosphorus source to the intermediate product is 50-200 mg:90-140 mg; In step 2), during the calcination, the phosphating atmosphere is an inert gas, the calcination temperature is 300-350° C., and the calcination time is 2-4 hours.

9. A copper-cobalt bimetallic phosphide heterojunction material prepared by the method according to any one of claims 1 to 8.

10. An application of the copper-cobalt bimetallic phosphide heterojunction material according to claim 9, characterized in that: The copper-cobalt bimetallic phosphide heterojunction material is used for electrocatalytic denitrification reaction.

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